A PRESENTATION ON SINGLE ELECTRON TRANSISTOR

By-:Shashank Joshi

OVERVIEWTransistorsClassification of transistorsA new field single electronicsPrinciple of single electronicsCoulomb blockadeSingle electron transistorsWorking of SETAdvantagesDisadvantagesApplicationsConclusion

TRANSISTORSA transistor is a three terminal,

semiconductor device which can be used for numerous purposes including signal modulation, amplification, voltage stabilization, and many others applications

Transistors are mostly used as switching devices in various circuits.

CLASSIFICATION OF TRANSISTORS TRANSISTORS

BJT FET

JFET MOSFET

MOSFET

A new field- Single ElectronicsThough the research stated in this field in

late 80’s, this field has still ways to go.

This field deals with the devices where we are able to control the movement and position of a single electron or a small number of electrons.

PRINCIPLES OF SINGLE ELECTRONICS

Orthodox Theory

Kondo effect

COULOMB BLOCKADE

The increase in resistance around zero bias i.e. the obstruction to the path of flow of electron is called coulomb blockade.

CONDITIONS FOR COULOMB BLOCKADEThe bias voltage must be lower than

the elementary charge divided by the self-capacitance of the island:

Vbias < e/C  

The thermal kinetic energy of the electron must be less than the Coulomb repulsion energy i.e.

kBT< e2/CThe tunneling resistance Rt should be greater

than h/e2.

SINGLE ELECTRON TRANSISTORSingle electron transistor is one of the most

important single electron device.

1.Three terminals with an island2.Island (30-50nm): A low self capacitance region3.Tuning by a Gate4.Relies on single electron tunneling through a nanoscale junction

WORKING OF SET For an electron to hop onto the island, its energy must equal

the Coulomb energy.

When both the gate and bias voltages are zero, electrons do not have enough energy to enter the island and current does not flow.

As the bias voltage between the source and drain is increased, an electron can pass through the island when the energy in the system reaches the Coulomb energy.

ADVANTAGESETs have very high switching speed as compared to BJTs

and MOSFETS.

SET working as a switching device, with transfer of only one electron, the device can be switched ON or OFF.

SETs have very low power consumption.

DISADVANTAGESVery low voltage gain.

Lithography techniques.

Room temprature operation.

Background charge.

APPLICATIONSSuper-sensitive electrometer.

Programmable single electron transistor logic.

Single electron memory.

Detection of microwaves.

Quantum Computers.

CONCLUSION At present research is going on for these

devices. Though good results have been received still there are formidable hurdles to cross. The future does look for these devices.

THANK YOU